In the field of aeronautics, parts made of composite and used to create an aircraft fuselage comprise lightning protection at their exterior surfaces. This lightening protection comprises at least one layer made of a material suited to affording lightening protection, such as, non limitingly, at least one layer of fiber glass fabric and/or a fine metal gauze.
This layer providing lightning protection is obtained by laying up a plurality of segments of tape, in juxtaposed manner, on a layup surface.
According to one way of packaging, the tapes comprise an interliner, for example made of paper, on one of their faces and are stored in spools. They have a given width of the order of 150 mm or 300 mm. These tapes are generally precut to form segments of tape which have a length and cuts at each of their ends that are suited to allowing the various segments of tape to be laid up one after another and/or one beside the next so that they cover the entire exterior surface of the component that is to be produced.
According to one procedure, the various segments of tape are laid up manually by operators on the layup surface which may be the surface of a tool or the surface of the last layer laid. To make the task easier, a laser projection assistance system is used to project the outlines of the various juxtaposed segments onto the layup surface.
This layup operation proves to be difficult to carry out on a layup surface of large surface area, such as a wing panel for example, and/or one which has a significant curvature, such as a fuselage segment for example.
The problem is that, for long length segments, it is essential that they be correctly oriented from the outset otherwise there will be a gap or an overlap with respect to the next segment which will increase as the laying of the segment processes. If the operator attempts to correct the orientation of the segment during the process of laying it up, creases may appear in the segment.
In the case of large surface areas, the operators cannot work ergonomically. In some instances, they are obliged to walk over the layup surface and possibly on the segments already laid up.
In order to create parts made of composite from carbon fiber pre-impregnated with resin, it is known practice to use layup machines for automatically laying up carbon fiber tapes which have been pre-impregnated with resin, packaged in the form of spools with an interliner on one of their faces. According to one embodiment illustrated in FIG. 1, a layup machine comprises a layup head 10 and a mechanism (not depicted) that allows the layup head 10 to be moved with respect to a layup surface 12 in a layup direction embodied by the arrow 14. The layup head 10 comprises a support configured to support a spool 16 from which a tape 18 to be laid up on the layup surface 12 is paid out, a layup roller 20 allowing the tape 18 to be pressed firmly against the layup surface 12. The layup head 10 also comprises a separation roller 22 that allows the interliner 24 to be removed from the tape 18 and a roller 26 that allows the interliner 24 to be stored in the form of a spool. The separation roller 22 is positioned between the spool 16 and the layup roller 20 and allows the interliner 24 to be removed before the tape 18 is compressed between the layup roller 20 and the layup surface 12. Thus, the tape 18 comprises a zone between the separation roller 22 and the layup roller 20 in which there is no interliner 24.
With this embodiment, the combination of the advancing movement of the layup head 10 and the action of compacting the tape 18 performed by the layup roller 20 allows tension to be applied to the tape 18, causing the paying-out from the spool 16.
This type of layup head is perfectly well suited to carbon fiber tapes which have a certain rigidity and good tensile strength.
Because lightning protection tapes do not have the same characteristics as carbon fiber tapes, this type of layup head is not suitable for laying them up automatically on a layup surface, the reasons being as follows:
In the absence of the interliner 24, the lightning protection tapes may deform locally, or even tear in the event of excessive tension. Now, as illustrated in FIG. 1, there is a zone 28 of tape between the separation roller 22 and the layup roller 20 which is separated from the interliner 24 and may undergo excessive tensile loading.
In addition, in the absence of the interliner 24, the lightning protection tape 18 does not have a certain rigidity. As a result, when a segment of the tape is completely separated from the interliner 24, a part 30 of said segment finds itself unsupported ahead of the layup roller 20. Insofar as this part 30 does not have a certain rigidity, it has a tendency to curl on itself ahead of the layup roller 20 and so is not correctly pressed firmly against the layup surface 12, as illustrated in FIG. 2.